Cylinder head

ABSTRACT

The present invention relates to an improvement in the internal combustion engine, particularly, internal combustion engines for automobiles. More specifically it relates to an improved cylinder head characterized by having the total area of the internal wall of the exhaust port constructed in two-piece fashion, one piece or part being a refractory part solidly enveloped with the other part which is the engine casting. The refractory part is shrinkfitted in the molten metal of the casting so that it can fully withstand repeated cycles of heating and cooling as well as mechanical vibrations.

United States Patent [191 Kaneko et al.

[ Jan. 22, 1974 CYLINDER HEAD Inventors:

Assignee:

Filed:

Appl. No.:

Yasuhisa Kaneko; Yasuhiko Komatsu; Yasuo Okada, all of Toyota, Japan Toyota .lidosha Kogyo Kabushiki Kaisha, Toyota-cho, Toyota-shi, Aichi-ken, Japan Nov. 14, 1972 Foreign Application Priority Data Nov. 30, 1971 Japan 46-96428 US. Cl....;. 123/193 11, 123/188 M, 123/191 A Int. Cl. F02b 23/00 Field of Search123/l93 H, 193 CH, 188 M, 191 A,l23/191 R, 193 R References Cited UNITED STATES PATENTS Kapraun 123/193 H 1,755,578 4/1930 Goldsborough 123/191 A 1,812,870 7/1931 Goldsborough 123/191 A 2,075,388 3/1937 De Cloud 123/191 A 2,154,717 4/1939 123/191 A 3,408,995 11/1968 Johnson 123/191 A FOREIGN PATENTS OR APPLICATIONS 665,330 l/l952 Great Britain 123/191 A Primary Examiner-Wendell E. Burns Attorney, Agent, or Firm-Arthur G. Connolly et al.

[57] ABSTRACT 2 Claims, 1 Drawing Figure CYLINDER HEAD BACKGROUND OF THE INVENTION The present invention relates to an improved cylinder head for an internal combustion engine.

Many attempts have been made to develope a device for the perfect combustion of gases to thereby eliminate the emission of unburnt gases. To mention a few typical examples, Japanese Utility Model Publication No. SHO 46-25927 discloses an engine emission gas purifier and Japanese Utility Model Publication No. SHO 46-31290 shows a particular exhaust manifold. The former represents an engine emission gas purifier using a tubular sleeve made of a heat-resistant and relatively less heat-conductive material than the engine case. The purifier is equipped with a heat-insulation air chamber at the back of the sleeve. This device, comprising a tubular sleeve within a purifier of prefabricated profile, cannot be applied to any complex part, and accordingly, high efficiency of purification is impossible. Moreover, for the purpose of increasing the purifying efficiency, the sleeve must be fabricated of expensive material, such as stainless steel or nickel alloy with a considerable thickness. If it is made of ceramic material, it will be subject to breakage under mechanical vibration. Furthermore, regardless of the material from which. it is made, considerable engineering is required to assure sealing of the air chamber.

The latter example represents an exhaust manifold provided with a ceramic lining. It is produced by preliminarily fabricating a manifold shell, providing the shell with a lining of compounded ceramic powder, and firing the entire assembly to consolidate the shell and lining. In the process of firing, however, the ceramic material contracts and often causes cracks to develop thereby resulting in an inferior product. This device is equally unfit for any complex part because it represents a prefabricated structure lined with heat-insulating material.

Thus, perfect elimination of unburnt harmful gases cannot be expected from any of the proposals so far made.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an improved cylinder head for an internal combustion engine that substantially eliminates the harmful emission of unburnt hydrocarbons.

The present invention comprises an improved cylinder head wherein the inner wall of the exhaust port is constructed in a double structure. The double structure may be a prefabricated refractory part placed in a casting mold and then enveloped in molten metal.

BRIEF DESCRIPTION OF THE DRAWING The sole FIGURE shows a longitudinal section of the exhaust port of a cylinder head fabricated according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION Referring in more particularity to the FIGURE, reference character 1 identifies a combustion chamber surrounded by a water-cooled jacket 2. An exhaust valve 3 is provided, and this valve cooperates with a valve seat 4. A guide 5 is provided for the stem of the exhaust valve 3. An exhaust port 6 comprises an aluminum casting 7 and a refractory part 8.

Auto emission gases include harmful components such as unburnt hydrocarbons, nitrogen oxides and carbon monoxide. These harmful emissions are one source of air pollution. The present invention is directed to reducing these harmful auto emission gases, and it accomplishes its objective through partial modification of the structure of the emission exhaust system of the engine.

For this purpose, according to the present invention the exhaust port of the cylinder head is lined with a refractory material thereby making the exhaust port a double structure. This construction contributes to reduction of the discharge of harmful auto emission gases, as explained more fully below.

The objective of reducing the discharge of harmful auto emission gases from the cylinder head of an internal combustion engine is attained according to the present invention for the following reasons:

1. the inner wall of the exhaust port is coated with a refractory material having a very low heat conductivity so that the emission gases remain hot, and as the result, the unburnt substances are oxidized;

2. since the refractory part has a large thermal capacity, the temperature drop in the inner wall of the exhaust port is minimized even if the emission gases are cooled by a change in operating conditions, and in consequence, the oxidization reaction is maintained; and

3. the refractory lining contains pores, and when the hot emission gases pass through these pores, a hot spot occurs at the pores and the oxidization reaction takes place.

The refractory materials available for the present invention include molten silica, high alumina, and

As explained above, the drawing shows a section of the exhaust system in a cylinder head equipped with a refractory part according to the present invention. A refractory part 8 about 45 mm thick is provided on the inside of the exhaust port 6. This refractory part is composed of SiO and A1 0,, at a 1:1 ratio. Its porosity is about 20 percent, its compressive strength 600 kglcm its specific heat 0.25 cal/g, and its heat conductivity is A cylinder head with such a refractory wall can be produced by placing a prefabricated refractory part in a cylinder casting mold, and then enveloping the refractory part in a molten metal for casting.

Next, the practical use of the cylinder head thus manufactured is described. The emission gases burned in the combustion chamber 1 are discharged through an opening between the exhaust valve 3 and the valve seat 4. in the conventional cylinder head, the emission gases, as they are, go out of the combustion chamber, and when the combustion in the chamber is incomplete, the unburnt gases pollute the air causing a public nuisance. When the device according to the present invention is adopted, the emission gases introduced into the exhaust port are partly oxidized and burned while passing through the port whereby the volume of harmful unburnt emission gases is drastically reduced. For instance, in the case of a 1,600 cc four-cycle gasoline engine equipped with the present cylinder head, in a test under the same conditions including acceleration and deceleration, approximately 50 percent of the unburnt harmful emission gases from a similar engine equipped with a conventional cylinder head are eliminated.

EXAMPLE 2 Utilizing the same procedure as in Example 1, a cylinder head was constructed for a 1,900 cc four-cycle gasoline engine. The exhaust port in the cylinder head was lined with a refractory wall 50 mm thick. The wall was fabricated of a high alumina substance with Al O over 98 percent characterized by a porosity of 1.8 percent, compressive strength 550 kg/cm specific heat 0.24 cal/g, and heat conductivity 0.60 Kcal/m.hr. C. The cylinder head was made of gray cast iron. Comparison with the conventional cylinder head under the same conditions as in Example 1 showed that the emission gases are reduced to about 40 percent.

The results of performance comparison test 3 of durability and purification between the improved cylinder head ofthe present invention and an exhaust duct heatinsulated by various conventional methods are shown in Table 2.

The tests were conducted using the engine of Example l with (l) the cylinder head of the present invention, (2) fitting a stainless pipe to the inner wall of the exhaust duct of the said engine, and (3) lining a ceramic material on the inner wall of the exhaust duct of the engine. The test condition was that the test should be conducted during 50 hours setting 6,000 r.p.m. full loaded l minutes after minutes idling as one cycle.

The device with the stainless pipe fitted to the inner wall of the exhaust duct has the disadvantage of low efpipe fitted to inner wall pipe was damaged.

oi'exhaust duct.

Device with a ceramic Over 2/1 portion of 45 15 material lined on the ceramic material was inner wall of exhaust damaged.

duet.

fect in purification performance. On the other hand, one advantage of the present invention is that the porous portion of the refractory product produces a hot spot so that the oxidization reaction may occur.

The device with ceramic material lined on the inner wall of the exhaust duct has the disadvantage of poor durability and remarkable lowering of exhaust gas purification after long use. On the other hand, the improved cylinder head of the present invention is characterized by improving the durability by enveloping the refractory product itself with the engine casting without lowering the purification performance.

The structure according to the present invention is equally advantageous with any internal combustion engine, for example, a rotary engine. Through adoption of the present invention, that is, by simply installing a double-structure exhaust port with a refractory wall, the harmful emission gases are drastically reduced, and this benefit can be obtained at low cost with no need for any special apparatus.

What is claimed is:

l. in a cylinder head of an internal combustion engine, the improvement comprising a cylinder head wherein the inner wall of the exhaust port of the head includes a prefabricated refractory insert in intimate engagement with the metal cylinder casting and around which the metal cylinder is cast whereby the refractory insert is under the compression of the surrounding metal.

2. The combination of claim 1 in which the refractory preform is fabricated from molten silica, high alumina or alumina-silica. 

1. In a cylinder head of an internal combustion engine, the improvement comprising a cylinder head wherein the inner wall of the exhaust port of the head includes a prefabricated refractory insert in intimate engagement with the metal cylinder casting and around which the metal cylinder is cast whereby the refractory insert is under the compression of the surrounding metal.
 2. The combination of claim 1 in which the refractory preform is fabricated from molten silica, high alumina or alumina-silica. 